A linear body having flexibility has been put into practical use as a linear medical appliance inserted in a vessel in a body. For example, a guide wire or a catheter inserted in a vessel in a body such as a blood vessel, a ureter, a bronchus, an alimentary canal, or a lymph vessel, or a wire having an embolization coil attached at a tip end for embolizing an aneurysm has been known. Such a linear body is inserted into a vessel in a body and guided to a destination through an operation from outside the body.
In many cases, the vessel in which the linear body is inserted is not necessarily linear but partially flexed or branched. In addition, a diameter of the vessel is not necessarily uniform, and the vessel itself may become thinner or a diameter of the vessel may be made smaller by an obstacle located in the vessel such as a thrombus in a blood vessel. A conventional linear body, however, has not been provided with means for sensing a condition in a direction of travel of the linear body, and it has been necessary to use operator's intuition in operating the linear body and the operator has had to be skilled in the operation for guiding the linear body from outside the body. A device provided with a pressure sensor at a tip end of a linear body is disclosed in Japanese Patent Laying-Open No. 10-263089 (Patent Document 1) as a device sensing presence of an obstacle in a direction of travel of the linear body.    Patent Document 1: Japanese Patent Laying-Open No. 10-263089